Dry hopping duration - Legitimate research

[kharper6]

As an ex-research assistant at my previous institution, I go nuts when I see excellent research dealing with my hobbies. Here is something long, but full of great tidbits :

http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/34093/Wolfe_thesis.pdf?sequence=1

I'm sure it has been seen before, but here is the tldr :

Dry hopping is better for flavor extraction, from a tasting level to a chemical analysis level. Dry hopping in an agitated system (stirring) is essentially complete after 24 hours, no more extraction occurred after 24 hours than 4 days, and beyond.

What does this mean for a homebrewer? Maybe not much, as I doubt any of us have a system to continually stir our beer. However, dry hopping for many days may not be the best thing. Just some thoughts to consider if you want a faster turn-around on your secondary with hopped beers.

"Another goal of this work was to closely examine the initial hours of dry
hopping to see whether shorter dry hopping times can be used while still extracting an acceptable amount of hop aroma. It is apparent from these data that whole cone hops benefit from longer contact time, but pellet hops were nearly fully-extracted after 24 hours" (Wolfe 63)

What do you guys think? I can somewhat relate to this, as an impatient brewer I've done some tasting tests with my recent IPA. I dry hopped it at 7 days. Took a small 2oz sample from it each day, stored it in the fridge. After 4 days, I sampled each of them and jotted my notes down. Day 1 showed mild bitterness/flavor additions, day 2/3/4 were all essentially identical.

I just added my second dry hop addition after kegging last night and I plan on doing the same.

 

[aiptasia]

There's one risk that I can think of. Agitating a finished beer by stirring it runs the risk of introducing oxygen into the beer, which will oxidize it creating an off flavor akin to wet leather or cardboard in the beer. You would have to devise a method of stirring without exposing the finished beer to oxygen. A simple CO2 purge might work just fine for that. If you keg your homebrew, you might be able to devise something simple.

 

[kharper6]

There's one risk that I can think of. Agitating a finished beer by stirring it runs the risk of introducing oxygen into the beer, which will oxidize it creating an off flavor akin to wet leather or cardboard in the beer. You would have to devise a method of stirring without exposing the finished beer to oxygen. A simple CO2 purge might work just fine for that. If you keg your homebrew, you might be able to devise something simple.

Typically when I do my secondary, I have a keg with 1 gallon of sanitizer in it that has been sitting for about 2-3 weeks. I give it a good 10 minute shake, roll, upside down, etc to ensure everything gets cover. Attach a 5' line to it, shoot some sanitizer out. tip it upside down, press the gas valve to get sanitizer through it, let out the 10lbs of pressure i put in it, empty it, then fill with beer, co2 purge, etc. I usually put my dry hops in a bag, tie it off with unflavored sanitized dental floss and run it up through the ball lock.

I guess mild agitation might help move things along, and I'd imagine it's safe considering there is no air leak.

Here is the method of agitation used in the research :

With this kind of hardware, I doubt they worried about oxygen

 

[aiptasia]

This powerhead would work because only the propeller portion of it is submersed. The backside of it has two powerful magnets that hold it in position, one inside & one outside. The power cord is on the outside portion and the amount of agitation can be tightly controlled for just the right amount of mix.

Insert the propeller side into a keg, connect it to the magnet through the wall of the keg, crank up the flow and drop in the hops. Then, seal the lid back on the keg and purge with CO2.

 

[unionrdr]

It's a misconception to think that dry hopping provides flavor. It's for aroma,but since our senses of taste & smell are limked by opennings in the roof of the mouth,aromas do give some perception of flavor. Our sense of smell adds to our sense of taste,in other words.